This invention relates to battery chargers in general, and in particular to battery chargers having means for indicating the polarity of connection of the charger and for indicating any voltage mismatch between the battery charger and battery.
When charging batteries of the type that are commonly used in automobiles, trucks and other vehicles, it is extremely important that a proper determination of polarity be made before the battery charger is actuated to charge a battery.
Furthermore, it is important to avoid arcing and sparks when battery terminals are connected to a battery because such arcing and sparks can ignite gases present within batteries, thereby causing dangerous explosions. Where the voltage of a charger and the battery are closely matched at the time of connecting clamps to the battery terminals, there is less likelihood of arcing and sparks than there would be if the voltage output of the battery charger is substantially greater than the battery voltage.
It is therefore important that both the polarity of connection and excesive differences in the voltages be indicated to the operator of a battery charger in order to minimize the risk of incorrect connection of a battery charger to a battery and to minimize the likelihood of a battery explosion.